They worry that enhanced waters (as they're called collectively) risk blurring the line between water and soda, and people will wind up drinking more sugar calories as a result. They also question whether the tantalizing extras - the vitamins, minerals and botanicals - do any good or could even cause harm.

"I don't know why people would want all those those things in their water," says Joanne Ikeda, co-director of the Center for Weight and Health at UC Berkeley.

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But they seem to. Even as Americans are guzzling bottled water as never before, including at restaurants (see Page E4), these enhanced waters are the fastest-growing part of that market - to the tune of $245 million wholesale last year, up from just $20 million when they debuted in 2000, according to research by Beverage Marketing Corp. in New York. And those who are their biggest fans are health-conscious young adults and baby boomers in trendy urban areas - such as the Bay Area - analysts say.

Propel, a fitness water from the makers of Gatorade, is by far the biggest- selling enhanced water, a low-calorie alternative to sports drinks.

Energy Brands' Glaceau Vitaminwater is scoring in the hipness market, with a dozen drinks in a rainbow of colors, each with a name that promises more than thirst relief - "determination," "focus" and "rescue," to name three. The Bay Area is one of the top markets, Glaceau's Oza says.

The beverages are so hot that Coke and Pepsi have followed the trend and added sugar, fruit flavors and vitamins to make enhanced versions of their Dasani and Aquafina waters. Even Anheuser-Busch, the beer giant, has been considering jumping in.

It's a logical progression from Americans' obsession with the plastic water bottle as a go-everywhere accessory. Americans are now spending $7.7 billion a year to hydrate; that's 21 gallons per person last year.

Whether or not humans really need 8 glasses of water a day (on top of the water they get from food and other drinks) is in dispute. Some doctors and the bottled water industry say so, but other doctors disagree. The National Academies of Science will deliver its opinion later this year. People believe it, though, and by the end of this year are expected to be drinking more bottled water than coffee, beer or milk - although water won't outrank soda pop.

Enhanced waters appeal to the core American desire for something "more," according to Tom Pirko, president of BevMark, food and beverage consultants in Santa Barbara. Americans turned to bottled water "not because we don't think our tap water is safe -- it has more to do with what else you can get," he says. Now it's enhanced waters.

BUZZWORDS

Executives for the enhanced waters tout them with words like "health," "pure," "natural," "two-in-one drinks" for consumers "who want more than pure hydration." Coke's Gloria Garrett described them as "emotional and functional" in a recent Beverage Industry trade magazine.

Oza says people don't drink enough water because they get bored -- but they'll drink more if its fun and flavored.

"People today are making purposeful choices about how they live and what they put in their body. They're fundamentally seeking a healthy lifestyle but not at the cost of giving up taste and variety," he says.

Pirko takes a more critical view.

"These waters are marketed to the vulnerable, the naive, the great mass of the population that lives with certain anxieties, a certain lack of confidence,

a certain set of dreams and ideals that (if they just drink this) they can be healthy or Arnold Schwarzenegger or Dubya -- that this will enhance their lives," Pirko says.

People who buy enhanced waters want to think they take a serious interest in their health when they don't, Pirko says. "If they did, they'd be eating their fruits and vegetables and drinking a lot of good water every day."

MORE STYLE THAN SUBSTANCE

All enhanced waters have water as the main ingredient. The subcategories vary more in marketing styles than in substance.

Most are lightly fruity and sweet -- either from sugar (Glaceau) or from a combination of sugar and the no-calorie sugar derivative sucralose (Propel, Hansen's). Some actually taste pretty much like water (Reebok). A few are superoxygenated.

Doses of vitamins and other additives go from low (25 percent of daily requirements for C, some of the Bs, E in Glaceau) to minuscule.

Botanical, herbal and other ingredients are added in various amounts. Inositol, taurine, carnitine, ginseng, guarana, glucosamine, gingko all crop up.

The concoctions raise a few questions for Ikeda and other nutritionists.

A main worry is added sugar.

If kids were switching from highly sugared sodas to enhanced waters, that might prove healthier. But, since the target market seems to be young and middle-aged adults, Ikeda thinks it's probably working the other way: Making even "water" sweet.

"Adding empty calories to the diets of children can be linked to the obesity that's epidemic. That's part of my concern -- that children are no longer drinking water, they're drinking sweetened beverages," she says.

HOW SWEET THEY ARE

A 20-ounce bottle of Glaceau vitaminwater has 125 calories' worth of sugar - - about half that of Coke. The other sugar-sweetened brands -- Aquafina Essentials, Dasani Nutriwater, Long Life's Enhance, have just a bit less.

Propel, with sucralose, has much less -- but still, it can train the taste buds to expect water to be sweet.

The vitamin load raises other questions.

One is legal, according to Ed Blonz, a nutritionist in Kensington. The waters fall under federal regulations governing food, not dietary supplements. Additives must be essential nutrients, or must be on a list approved as "generally regarded as safe." But gingko and some of the others aren't, Blonz says.

NO SMOKING

The FDA did take action when a nicotine-laced water hit the market, but hasn't otherwise interfered with enhanced waters.

"What it comes down to is, are they going to hurt people? They're not dangerous," Blonz believes. But he adds, "Are they going to help you? It's doubtful."

Another question is if guzzlers risk overdosing on vitamins.

Ikeda says that mostly water-soluble vitamins are involved, so kidneys can work harder and excrete the excess. But some are fat-soluble and stored in the body.

"There's no doubt that with all the fortified foods and supplements available today, people can get close to toxic levels, if you just keep adding up these 25 percents," she warns. "It's of real concern: How much are you really getting?"

As far as the more exotic ingredients go, she says, it's anyone's guess what they do in the body -- or how they may interact. She thinks eating varied,

healthy foods is a better way to get what human bodies need.

DRINKING THE UNKNOWN

"To me, it's so ridiculous that people are drinking things with compounds that they don't even know if they're helpful or harmful," says Ikeda.

Whether enhanced waters are a flash in the pan or the next Snapple is hard to know, says analyst Gary Hemphill at Beverage Marketing Corp.

But no matter what, Pirko says Americans are just at the beginning of the nutraceutical beverage and food era.

"Anything that adds some dimension of interest, of assumed benefit, of excitement -- I think we're just starting out on that."

Dasani NutriWater, Coca-Cola. 20 calories per 8 ounces. Being test-marketed elsewhere and not yet available in Northern California. Four flavors with combinations of B, C and E vitamins, calcium and magnesium.

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